Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.57	5.191%	$181.5281	$181.53	$181.55	$181.50
Purchase #2	$229.54	11.716%	$256.4329	$256.43	$256.45	$256.40
Purchase #3	$12.82	6.709%	$13.6801	$13.68	$13.70	$13.70
Purchase #4	$73.54	13.275%	$83.3024	$83.30	$83.30	$83.30
Purchase #5	$234.87	12.397%	$263.9868	$263.99	$264.00	$264.00
Purchase #6	$246.65	3.571%	$255.4579	$255.46	$255.45	$255.50
Purchase #7	$237.82	7.362%	$255.3283	$255.33	$255.35	$255.30
7 purchase totals =	$1,207.81		$1,309.7165	$1,309.72	$1,309.80	$1,309.70